Fuel system for a combustion driven fastener hand tool

ABSTRACT

A combustion driven fastener hand tool is disclosed having a fuel system subassembly including a fuel nozzle and a metering valve, disposed in a common bore of the combustion driven fastener apparatus. The metering valve comprises a hollow cylindrical housing having a cap at each end and a central dual valve stem therebetween. Movement of the dual central valve stem closes an inlet valve at one end and opens an outlet valve at an opposite end in a coordinated manner to release a metered amount of fuel through the outlet valve while preventing additional fuel through the inlet valve. The combustion driven fastener hand tool includes numerous other features affording improvements over the prior art.

CROSS-REFERENCE TO RELATED APPLICATIONS

This continuation application claims the benefit under 35 § 120 of thefollowing co-pending and commonly assigned U.S. utility patentapplication:

U.S. patent application Ser. No. 14/839,765, filed Aug. 28, 2015 andentitled “COMBUSTION DRIVEN FASTENER HAND TOOL.” by Wong et. al.(Attorney Docket GREXP002) which application claims the benefit of U.S.Provisional Patent Application No. 62/043,279, filed Aug. 28, 2014, andentitled “COMBUSTION DRIVEN FASTENER HAND TOOL,” by Wong et al.(Attorney Docket GREXP002.P1), which applications are both incorporatedby reference herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to powered fastener driving hand tools.Particularly, this invention relates to a combustion driven fastenerhand tool.

2. Description of the Related Art

Powered fastener driving tools, e.g. nail guns, have existed fordecades. Perhaps not coincidentally, the first commercial nail gun wasintroduced in 1950 after World War II wherein the technology for rapidlyfiring projectiles was greatly advanced. The first nail guns werepneumatic, driven by compressed air. Although pneumatic power is stillthe most prevalent, over time fastener driving tools have been developedusing other means of power, such as electric motors, solonoids,combustibles, e.g. gas or explosive powder, have also been developed.Some development of technology related to powered fastener drivers, andparticularly combustion driven fastener tools. However, there is stillmuch need for further development.

U.S. Patent Application Publication No. 2012/0210974, published Aug. 23,2012, by Adams, discloses a gas-powered tool motor includes a combustionchamber with an intake valve at one end, an exhaust valve at anotherend, and a control plate or control valve between two portions of thecombustion chamber A piston or other positive displacement device is incommunication with the combustion chamber. The intake and exhaust valveshave closure members that are movable along a common axis in tandembetween collective open positions for recharging the combustion chamberwith the fuel and air mixture and collective closed positions fordetonating the fuel and air mixture in the combustion chamber anddisplacing the positive displacement device. The control plate orcontrol valve supports limited air flows from a first portion of thecombustion chamber to a second portion of the combustion chamber even inthe closed position of the control valve for supporting two-stagecombustion.

In view of the foregoing, there is a need in the art for apparatuses andmethods improving the operation of combustion driven fastener handtools. There is also a need for such apparatuses and methods thatoperate reliably and efficiently over many uses and at a reduced cost.In addition, there is a need for such apparatuses and methods to allowcomfortable and precise control of combustion driven fastener handtools. There is further a need for such systems and apparatuses to beinexpensively manufacturable and readily servicable. These and otherneeds are met by the present invention as detailed hereafter.

SUMMARY OF THE INVENTION

A combustion driven fastener hand tool is disclosed having a fuel systemsubassembly including a fuel nozzle and a metering valve, disposed in acommon bore of the combustion driven fastener apparatus. The meteringvalve comprises a hollow cylindrical housing having a cap at each endand a central dual valve stem therebetween. Movement of the dual centralvalve stern closes an inlet valve at one end and opens an outlet valveat an opposite end in a coordinated manner to release a metered amountof fuel through the outlet valve while preventing additional fuelthrough the inlet valve. The combustion driven fastener hand toolincludes numerous other features affording improvements over the priorart.

A typical combustion hand tool embodiment of the invention comprises acombustion driven fastener apparatus, including a front body sectionincluding a first bore and a second bore comprising a combustionchamber, the first bore parallel to the second bore, where a passagecouples the combustion chamber to the first bore at an end of the firstbore, a piston disposed in the first bore to drive a fastener, and aprimary housing comprising a left half and a right half enclosing thefront body section. The combustion driven fastener apparatus is capableof having a fuel and air mixture driven under pressure into thecombustion chamber and ignited to generate pressure through the passageand force the piston in the first bore to drive the fastener. Typically,the front body section comprises an extruded component and the left halfand the right half of the primary housing comprise cast components. Theleft half and the right half of the primary housing and the front bodysection can comprise aluminum.

In some embodiments, the front body section can include a third borecomprising a pathway for the fuel and air mixture to the combustionchamber. Alternately, a pathway for the fuel and air mixture to thecombustion chamber can be formed by attaching a crescent piece to anouter wall of the second bore of the front body section.

In further embodiments, the front body section can include a railparallel to the first bore and the second bore, the rail engaging anouter housing having one or more mating slots to the rail.

In some embodiments, a hand grip section can also be included having afuel system bore for housing fuel system components of the combustiondriven fastener apparatus. The hand grip section comprises an extrudedcomponent.

In a similar manner, a typical method embodiments of the inventioncomprises making a combustion driven fastener apparatus, includingextruding a front body section including a first bore and a second borecomprising a combustion chamber, the first bore parallel to the secondbore, where a passage couples the combustion chamber to the first boreat an end of the first bore, disposing a piston in the first bore todrive a fastener, casting a primary housing comprising a left half and aright half, and enclosing the front body section with the left half andthe right half of the primary housing. The combustion driven fastenerapparatus is capable of having a fuel and air mixture driven underpressure into the combustion chamber and ignited to generate pressurethrough the passage and force the piston in the first bore to drive thefastener. This method embodiment can be further modified consistent withany of the apparatuses described herein.

In a similar manner, a combustion driven fastener apparatus embodimentof the invention can include a front body section including a first boreand a second bore comprising a combustion chamber means for temporarilyholding and directing a fuel and air mixture as it combusts to generatepressure, the first bore parallel to the second bore, where a passagecouples the pressure from the combustion chamber means to the first boreat an end of the first bore, a piston means for driving a fastener underthe pressure from the fuel and air mixture combusting, the piston meansdisposed in the first bore, and a primary housing means for enclosingthe front body section. This apparatus embodiment can be furthermodified consistent with any of the apparatuses and/or methods describedherein.

Another embodiment of the invention comprises a combustion drivenfastener apparatus, including a sliding link disposed in a channel of anose piece of the combustion driven fastener apparatus and an armaturerotatable about a pinned joint, the armature having a first arm coupledto the sliding link by a slotted joint and a second arm arranged tooperate a fuel charging valve of the combustion driven fastenerapparatus. Pressing the nose piece against a surface moves the slidinglink coupled to the first arm of the armature by the slotted jointrotating the armature which causes the second arm to operate the fuelcharging valve. Typically, the sliding link is trapped in the channel ofthe nose piece such that the sliding link is movable a limited distancein one dimension. The fuel charging valve can be spring loaded againstthe second arm in order to return the armature and in turn the slidinglink to respective starting positions after the nose piece is no longerpressed against the surface. The slotted joint can comprise a rollerbushing coupled to the sliding link which rolls in a slot in the firstarm of the armature. In addition, the second arm of the armaturecomprises two parallel extensions connected by an axial extensionproximate the pinned joint. The pinned joint can comprise two screwscollinearly aligned with one through each parallel extension and a wideroller bushing can be coupled between ends of the two parallelextensions. The wide roller bushing can be disposed against an operatinglever of the fuel charging valve.

Similarly, another embodiment of the invention comprises a method ofmaking a combustion driven fastener apparatus, including disposing asliding link in a channel of a nose piece of the combustion drivenfastener apparatus, and pinning an armature to be rotatable about arotational joint, the armature having a first arm coupled to the slidinglink by a slotted joint and a second arm arranged to operate a fuelcharging valve of the combustion driven fastener apparatus. Pressing thenose piece against a surface moves the sliding link coupled to the firstarm of the armature by the slotted joint rotating the armature whichcauses the second arm to operate the fuel charging valve. This methodembodiment can be further modified consistent with any of theapparatuses described herein.

Yet another embodiment of the invention comprises an igniter for acombustion driven fastener apparatus including a housing including alongitudinal section and a transverse section, a switch for triggering aspark to be generated at the ignition spark point the switch disposed atan end of the longitudinal section, and a conductor within thetransverse section having a spark point exposed at an end of thetransverse section of the housing, the transverse section comprising anelectrical insulator. The remote ignition control electronics can beelectrically coupled to the conductor and the switch and send a highvoltage pulse to the spark point of the conductor to generate the sparkin response to receiving a trigger signal from the switch.

In addition, the switch can comprise an optical switch that is openedand closed by allowing and preventing light to contact a detector. Theoptical switch can include a spring loaded movable component having awindow therethrough in front of the detector. The spark can be generatedbetween the spark point and an edge of a disc affixed to a valve sternwithin a chamber of the combustion driven fastener apparatus. The disccan be tapered to an edge at an outer diameter. Movement of the valvestem can operate at least one valve of the chamber such that the disc isdisposed proximate to the spark point after the valve stem is positionedto close the at least one valve. Typically, the spark point is disposedproximate to an end of the chamber. The stern and the disc areelectrically conductive to close a circuit allowing the spark to begenerated.

Similarly, another embodiment of the invention comprises a method ofmaking an igniter for a combustion driven fastener apparatus, includingproducing a housing including a longitudinal section and a transversesection, the transverse section comprising an electrical insulator,disposing a switch at an end of the longitudinal section, the switch fortriggering a spark to be generated at the ignition spark point, anddisposing a conductor within the transverse section having a spark pointexposed at an end of the transverse section of the housing. This methodembodiment can be further modified consistent with any of theapparatuses described herein.

Yet another embodiment of the invention comprises a combustion drivenfastener apparatus, including a front cover of a hand grip having ahinged engagement to a back portion of the hand grip along a side of thefront cover, the hinged engagement allowing both rotational movementabout a hinge axis and axial movement along the hinge axis of the frontcover, and a catch disposed in the back portion on the opposite side ofthe hinged engagement for releasably engaging the front cover of thehand grip after the front cover is rotated about the hinge axis, closedagainst the back portion, and moved axially along the hinged axis. Aninterior pocket of the front cover of the hand grip can support a fuelcartridge for the combustion driven fastener apparatus. The front covercan be designed such that axial movement of the front cover along thehinged axis pushes the fuel cartridge such that a valved port of thefuel cartridge engages a mating port within the hand grip.

In further embodiments, a feature can be disposed on the front cover onan opposite side of the hinged engagement, and a mating feature disposedon the back portion of the hand grip on the opposite side of the hingedengagement, wherein the feature engages the mating feature after thefront cover is rotated about the hinge axis, closed against the backportion, and moved axially along the hinged axis and engagement of thefeature and mating feature prevents rotational movement about the hingeaxis but allows axial movement along the hinge axis. The feature cancomprise a pin extending from the front cover on an opposite side of thehinged engagement and parallel to the hinge axis and the mating featurecan comprise a hole in the back portion of the hand grip. The pinengages a hole in the back portion of the hand grip after the frontcover is rotated about the hinge axis, closed against the back portion,and moved axially along the hinged axis. The catch can comprise a springloaded button catch.

Similarly, another embodiment of the invention comprises a method ofmaking a combustion driven fastener apparatus, including producing afront cover of a hand grip having a hinged engagement to aback portionof the hand grip along a side of the front cover, the hinged engagementallowing both rotational movement about a hinge axis and axial movementalong the hinge axis of the front cover, and disposing a catch in theback portion on the opposite side of the hinged engagement forreleasably engaging the front cover of the hand grip after the frontcover is rotated about the hinge axis, closed against the back portion,and moved axially along the hinged axis. This method embodiment can befurther modified consistent with any of the apparatuses describedherein.

Another embodiment of the invention comprises a combustion drivenfastener apparatus, having a fuel system subassembly including a fuelnozzle having a metered fuel input port and fuel and an air mixtureoutput port, the fuel nozzle disposed in a bore of the combustion drivenfastener apparatus, and a metering valve having a fuel input port and ametered fuel output port, the metering valve disposed in the bore withthe metered fuel output port coupled to the metered fuel input port, themetering valve comprising a hollow cylindrical housing having a cap ateach end and a central dual valve stem therebetween. Movement of thedual central valve stem closes an inlet valve at one end and opens anoutlet valve at an opposite end in a coordinated manner to release ametered amount of fuel through the outlet valve while preventingadditional fuel through the inlet valve. The bore can include a step tolocate the metering valve at a set position along a length of the bore.The fuel nozzle and the metering valve can be cylindrically configuredwith the metering valve having a larger maximum diameter than the fuelnozzle. The bore can be disposed in a hand grip section of thecombustion driven fastener apparatus. The cap at each end can comprise acommon cap design having an annular groove.

In further embodiments, the fuel system subassembly can include abiasing spring disposed between the fuel nozzle and the metering valveand moving the fuel nozzle towards the metering valve compresses thebiasing spring therebetween such that the metered fuel input port of thefuel nozzle pushes against the metered fuel output port of the meteringvalve causing the movement of the dual central valve stem. The dualcentral valve stem can be configured such that fuel pressure behind thefuel input port of the metering valve can forces the dual central valvestem such the that inlet valve is normally open and the outlet valve isnormally closed. The fuel system subassembly can further include apressure regulator having a fuel cartridge input port and a fuel outputport, the pressure regulator disposed in the bore with the fuel outputport coupled to the fuel input port of the metering valve.

In further embodiments, a cap fastened over the bore in the hand gripsection can be used to secure the fuel system subassembly in place, thecap including a clip portion extending from an end of the hand gripsection adjacent and parallel along a side of the hand grip section. Thecap can be fastened over the bore by a plurality of screws in asymmetric pattern such that the cap can be secured in two alternateorientations, one with the clip portion along a left side of the handgrip section and another with the clip portion along a right side of thehand grip section.

Similarly, another embodiment of the invention comprises a method ofmaking a combustion driven fastener apparatus, comprising a fuel systemsubassembly including disposing a fuel nozzle in a bore of thecombustion driven fastener apparatus, the fuel nozzle having a meteredfuel input port and fuel and an air mixture output port, and disposing ametering valve in the bore behind the fuel nozzle with the metered fueloutput port coupled to the metered fuel input port, the metering valvehaving a fuel input port and a metered fuel output port, the meteringvalve comprising a hollow cylindrical housing having a cap at each endand a central dual valve stem therebetween. Movement of the dual centralvalve stem closes an inlet valve at one end and opens an outlet valve atan opposite end in a coordinated manner to release a metered amount offuel through the outlet valve while preventing additional fuel throughthe inlet valve. This method embodiment can be further modifiedconsistent with any of the apparatuses described herein.

Another embodiment of the invention comprises a combustion drivenfastener apparatus, including a front body section including a firstbore and a second bore together comprising a combustion chamber, thefirst bore parallel to the second bore, where a passage couples thecombustion chamber to the first bore at an end of the first bore, apiston and driver disposed in the first bore to drive a fastener, avalve stem assembly disposed in the second bore to control fuel chargingof combustion chamber, and a top cap assembly fastened to the front bodysection over the first bore and the second bore. The piston and driverare removable from the first bore and the valve stem assembly isremovable from the second bore after unfastening the top cap assembly.Typically, a conductor is disposed in a wall of the second bore of thecombustion chamber such that the conductor does not interfere withremoval of the valve stem assembly. The valve stem assembly can includea disc affixed to a central stem that is electrically coupled to a sparkgenerator such that a spark can be generated between the disc and theconductor.

In further embodiment piston bumper can be disposed in the first borebehind the piston and driver, the piston bumper having a groove forengaging an edge of a clip installed through a slot in a side of thefront body section. Typically, the piston bumper comprises anelastomeric material. The edge of the clip can comprise an interiorsemi-circular edge and the piston bumper can comprise a cylindricalshape with the groove disposed around an outer circumference of thecylindrical shape.

Similarly, another embodiment of the invention comprises a method ofmaking a combustion driven fastener apparatus, comprising producing afront body section including a first bore and a second bore comprising acombustion chamber, the first bore parallel to the second bore, where apassage couples the combustion chamber to the first bore at an end ofthe first bore, disposing a piston and driver in the first bore to drivea fastener, disposing a valve stem assembly in the second bore tocontrol fuel charging of combustion chamber, and fastening a top capassembly to the front body section over the first bore and the secondbore. The piston and driver are removable from the first bore and thevalve stem assembly is removable from the second bore after unfasteningthe top cap assembly. This method embodiment can be further modifiedconsistent with any of the apparatuses described herein.

Yet another embodiment of the invention comprises a combustion drivenfastener apparatus, including a valve stem disposed in a combustionchamber, a disc affixed to the valve stem, and a conductor having aspark point disposed in a wall of the combustion chamber. A spark isgenerated between the spark point and an edge of the disc to ignitecombustion with the combustion chamber. Typically, the disc is taperedto an edge at an outer diameter and the conductor does not extend intothe combustion chamber allowing removal of the vale stem from one end ofthe combustion chamber without moving the conductor. The valve stem canbe movable with the combustion chamber to operate at least one valvesuch that the disc is disposed proximate to the spark point after thevalve stern is positioned to close the at least one valve. The sparkpoint is typically disposed proximate to an end of the chamber and thevalve stern and the disc are electrically conductive to close a circuitallowing the spark to be generated.

Similarly, another embodiment of the invention comprises a method ofmaking a combustion driven fastener apparatus, comprising affixing adisc to a valve stem, disposing the valve stem in a combustion chamber,and disposing a conductor in a wall of the combustion chamber, theconductor having a spark point at an end exposed to the combustionchamber. A spark is generated between the spark point and an edge of thedisc to ignite combustion with the combustion chamber. This methodembodiment can be further modified consistent with any of theapparatuses described herein.

Yet another embodiment of the invention comprises a combustion drivenfastener apparatus, including a front body section including at leastone bore comprising a combustion chamber and a T-rail disposed on anexterior surface of the front body section and parallel to the at leastone bore, and an exterior housing comprising a left portion and a rightportion enclosing the front body section, the left portion having a leftgroove to engage a left side of the Trail of the front body section andthe right portion having a right groove to engage a right side of theT-rail of the front body section. Typically, the exterior housingcomprises a plastic part and the front body section comprises anextruded metal part.

In further embodiments a primary housing including a left side and aright side, the left side and the right can enclose the front bodysection on either side of the T-rail with the T-rail extending past anexterior surface of the primary housing to engage the left groove andthe right groove of the exterior housing. Typically, the primary housingcomprises a cast metal part. The front body section can comprise anexterior surface having one or more reed valves affixed to the exteriorsurface adjacent to and covering one or more exhaust ports and one ormore standoffs on an interior surface of the exterior housing preventsthe one or more reed valves from opening too far causing permanentdeformation of the one or more reed valves.

Similarly, another embodiment of the invention comprises a method ofmaking a combustion driven fastener apparatus, comprising forming aT-rail on an exterior surface of a front body section, the front bodysection including at least one bore comprising a combustion chamber andthe T-rail being parallel to the at least one bore a front body section,and enclosing the front body section with an exterior housing comprisinga left portion and a right portion, the left portion having a leftgroove to engage a left side of the T-rail of the front body section andthe right portion having a right groove to engage a right side of theT-rail of the front body section. This method embodiment can be furthermodified consistent with any of the apparatuses described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIGS. 1A-1E illustrate front, side, bottom, top, and isometric views,respectively, of an exemplary combustion driven fastener hand toolembodiment of the invention;

FIGS. 2A-2E illustrate exploded, cross section, and assembly views ofthe primary housing, front body section, and hand grip section of anexemplary combustion driven fastener hand tool embodiment of theinvention;

FIGS. 3A and 3B illustrate detailed views of the front body section ofan exemplary combustion driven fastener hand tool embodiment of theinvention;

FIGS. 4A and 4B illustrate detailed views of the front body section railand attachment to the housing of an exemplary combustion driven fastenerhand tool embodiment of the invention;

FIGS. 5A-5C illustrate detailed views of the fuel cartridge housing andhand grip assembly of an exemplary combustion driven fastener hand toolembodiment of the invention;

FIG. 6A illustrates a bi-directional belt clip assembly of an exemplarycombustion driven fastener hand tool embodiment of the invention;

FIGS. 6B-6E illustrate detailed views of a fuel mixing and transportassembly of an exemplary combustion driven fastener hand tool embodimentof the invention;

FIGS. 7A and 7B illustrate cutaway views of a fuel charging operation ofan exemplary combustion driven fastener hand tool embodiment of theinvention;

FIG. 7C illustrates an integrated ignition switch and spark point of anexemplary combustion driven fastener hand tool embodiment of theinvention;

FIG. 8 illustrates a dual chamber assembly of an exemplary combustiondriven fastener hand tool embodiment of the invention;

FIGS. 9A-9C illustrates a unitary fuel passage baffle of an exemplarycombustion driven fastener hand tool embodiment of the invention;

FIG. 10 illustrates an ignition battery compartment and access of anexemplary combustion driven fastener hand tool embodiment of theinvention;

FIG. 11 illustrates replaceable piston bumper element of an exemplarycombustion driven fastener hand tool embodiment of the invention;

FIGS. 12A-12C illustrate exhaust valves of an exemplary combustiondriven fastener hand tool embodiment of the invention; and

FIGS. 13A-13D illustrate fuel charging, safety linkage and triggerlockout of an exemplary combustion driven fastener hand tool embodimentof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

1. Overview

As previously mentioned, embodiments of the invention are directed to acombustion driven fastener hand tool having an extruded front bodycomponent including two to three primary bores. A first bore forms acylinder for the piston which drives the fastener. A second bore forms aprimary combustion chamber in which a fuel and air mixture is ignitedand directed into the adjacent piston cylinder. The extruded front bodycomponent can be enclosed in two cast primary housing pieces. Anexterior housing, e.g. which may be molded plastic, then encloses theentire assembly. A novel “T-rail” of the front body section slides intoa matching slot on the exterior housing. The combustion driven fastenerhand tool includes numerous other features affording improvements overthe prior art.

Embodiments of the invention can implement many improvements in thenovel front body section of the combustion driven fastener hand tool.Within the front body section embodiments of the invention can employ areadily replaceable piston driver and piston bumper for combustiondriven fastener hand tool. The piston driver is readily accessible froma single removable top cap assembly. After removing the piston driver,the piston bumper is easily removable, held in place by a simple clip.Novel exhaust valves can also be employed into a front body sectionhaving stops integrated into an exterior housing of a combustion drivenfastener hand tool.

In addition, embodiments of the invention can employ a novel integratedhand grip and fuel system designed for easy serviceable access and fuelcartridge replacement in a combustion driven fastener hand tool. Anintegrated igniter switch and spark point can also be employed and canoperate with a novel disc on a fuel valve stem to create the spark gapfor ignition. A novel, simple and versatile unitary fuel passage bafflecan also be employed. Embodiments of the invention can also employ anovel integrated ignition battery compartment and structure support forcombustion driven fastener hand tool. A novel fuel charging safetylinkage can also be implemented in a combustion driven fastener handtool.

FIGS. 1A-1E illustrate front, side, bottom, top, and isometric views,respectively, of an exemplary combustion driven fastener hand toolembodiment of the invention. The exemplary combustion driven fastenerhand tool 100 includes a front body 102 which houses the piston andcombustion chambers. A grip portion 104 and a trigger 106 extend fromthe front body 102. The grip portion 104 is held by the user duringoperation. The grip portion 104 also encloses a fuel cartridge andincludes a pressure regulator and fuel mixing components of the fuelsystem. A fastener strip carrier 108 is disposed laterally from one endof the front body 102. Typically, a fastener strip comprises a series ofseparate slender metal fasteners disposed side by side and lightlybonded together, e.g. by a tape layer, as is known in the art. A batterycarrier section 110 extends from the end of the grip portion 104 towardsthe end of the fastener strip carrier 108. Additional structural supportis afforded by a bracket 112 coupled between the battery carry section110 and the fastener strip carrier 108.

It should be noted that multiple example detailed designs are shown inthe accompanying figures in order illustrate the various inventiveaspects. For example, variations on the different housings may beillustrated. However, the relevant inventive features are not limited toany particular design unless otherwise noted.

2. Body Structure for Combustion Driven Fastener Hand Tool

As previously mentioned, embodiments of the invention can incorporate anumber of novel features into a front body section of an combustiondriven fastener band tool. Embodiments of the invention can incorporatean efficient arrangement of components of four principle sections whichenables lower cost manufacturing and the production of more accurate,precise parts which also provides for better alignment of the parts. Twoof the four elements can be cheaply manufactured as extruded components,a front body section for the piston and combustion chambers and a handgrip section for the fuel delivery and mixing components. The extrudedfront body and hand grip sections are enclosed by two cast halves of theprimary housing. In general, the number of critical dimensions affectingthe function and performance of the device is reduced and isolated tothe extruded elements. Accordingly, this arrangement arrangement ofcomponents leads to improved function and reliability and greatlyreduced overall cost of the tool.

FIGS. 2A-2E illustrate exploded, cross section, and assembly views ofthe primary housing 204A, 204B, front body section 202, and hand gripsection 206 of an exemplary combustion driven fastener hand tool 200embodiment of the invention. The front body section 202 is enclosedwithin two halves of primary housing 204A, 204B. See FIGS. 2A-2B. Theprimary housing 204A, 204B can also enclose the hand grip section 206.Manufacturing costs are reduced by employing extrusions for the frontbody section 202 and the hand grip section 206 and a casting for theprimary housing 204A, 204B. See FIGS. 2C-2E. The extruded hand gripsection 206 comprises a bore which is used to house the fuel meteringand mixing components as described hereafter. All parts can be producedfrom aluminum or any other suitable material known in the art.

One important aspect employed in embodiments of the invention involves afront body section. This component can be readily produced as anextruded element, e.g. from aluminum, with minimal finish machining andincludes three parallel bores through its length. A first bore forms thecylinder for the piston which drives the fastener, a second bore formsthe primary combustion chamber, and a third bore forms a fuel mixtureflow path. Typically, the piston cylinder and the combustion chamberbores are cylindrical whereas the fuel mixture flow path bore is“quasi-crescent” shaped, disposed along a portion of the outer surfaceof the combustion chamber bore. In an alternate embodiment the frontbody section may be extruded having two parallel bores, a first boreforming the cylinder for the piston which drives the fastener and asecond bore forming the primary combustion chamber. In this case, thefuel mixture flow path adjacent o the combustion chamber is formed byattaching a separate crescent shaped component to the extrudedcomponent. Forming the front body section as an extruded part having atleast two parallel bores affords an inexpensive, yet precise part.

FIGS. 3A and 3B illustrate detailed views of the front body section 202of an exemplary combustion driven fastener hand tool embodiment of theinvention. As previously described, the front body section 202 comprisesup to three bores which can be inexpensively manufactured as an extrudedpart. A first bore 304 is used for the piston (which may be alternatelydescribed as a secondary combustion chamber). A second bore 306 is usedas the primary combustion chamber. The first and second bores 304, 306are substantially cylindrical. An optional third bore 308 can also beformed having a crescent shape which is used as a fuel and air mixturepathway to the primary combustion chamber. See FIG. 3A. Instead of thethird bore 308, the fuel and air mixture pathway can be alternatelyformed as a separate crescent shape part 310 which is attached to theouter wall of the second bore 306.

The front body section 202 can also be extruded to include a “T-rail”section 302 parallel and adjacent to the piston bore. This T-rail 302 isused to couple to an exterior housing of the complete hand tool assembly(which covers the cast primary housing halves). Incorporating the T-rail302 in the front body section allows for quick assembly/disassembly andalignment of components without adding any cost, i.e. no additionalfasteners or machining, as would be required with a cast part instead ofan extrusion. The T-rail 302 is produced as part of the overallextrusion. The exterior housing includes matching slots which engage theT-rail 302 secure the exterior housing over the cast primary housinghalves. It should be noted that rail 302 need not be configured as a“T”; other rail geometries may also be used provided matching slots areproduced on the exterior housing parts.

FIGS. 4A and 4B illustrate detailed views of the rail 302 of the frontbody section 202 and attachment to the exterior housing 402A, 402B of anexemplary combustion driven fastener hand tool embodiment of theinvention. The rail 302 built into the front body section 202 is used tosecure and align together the front body section 202 with the primaryhousing 204A, 204B and the exterior housing 402A, 402B. The halves ofthe exterior housing 402A, 402B is nested over the primary housing 204A,204B and have slots which engage the rail 302 of the front body section202.

3. Hand Grip and Fuel System for Combustion Driven Fastener Hand Tool

Embodiments of the invention can employ a pressurized liquid fuelcartridge, e.g. propane, which can be readily purchased off the shelfand replaced by the user. The fuel cartridge is cylindrical having avalved port at the center of one end of the cylinder. It should be notedthat embodiments of the invention are not limited to any particular fueland the inventive concepts described herein can be readily adapted to arange of suitable combustible fuels as will be appreciated by thoseskilled in the art.

Another important feature of an embodiment of the invention involves thefuel storage and delivery components of the hand tool. The standardizedfuel cartridge loading is conveniently loaded and unloaded from the toolusing a storage compartment and loading/unloading mechanism integratedinto the hand grip of the tool. The front portion of the hand grip(whereon the user's fingers rest in use) is hinged along one side andincludes spring loaded button catch on the opposite side. In addition torotation about the hinge axis, the hinge design allows for somedisplacement along the hinge axis. The hand grip cover is fully openedby first releasing the spring loaded button catch, sliding the coverforward along the hinge axis and then opening the hand grip cover byrotating it about the hinge axis.

FIGS. 5A-5C illustrate detailed views of the fuel cartridge housing andhand grip assembly of an exemplary combustion driven fastener hand toolembodiment of the invention. The grip portion 104 of the hand toolincorporates the fuel cartridge storage which is accessed by a hingedhand grip cover 502. The hinge 504 can comprise aligned pins 506A, 506Bpressed into the hand grip cover 502 along one edge. The hinge 504 isdesigned to allow some movement along the hinge axis when installed. Analigning pin 508 (which extends from the cover a shorter length than theallowed axial movement of the hinge 504) is disposed on one side of theopposing edge of the hand grip cover 502. In use, the hand grip cover502 is first closed and then moved along the hinge axis such that thealigning pin 508 engages a hold in the grip portion 104 of the handtool. When the aligning pin 508 is fully engaged and the hand grip cover502 is seated against its bottom edge, a spring loaded button catch 210becomes aligned with an engaging feature in the cover 502 andautomatically latches to secure the cover 502 closed. With a fuelcartridge placed into the cover 502, this same process serves to loadthe cartridge into the hand tool as described hereafter.

When loading a fuel cartridge, with the hand grip cover open, a fuelcartridge is placed in the interior pocket of the hand grip cover (withthe port towards the end of the hand grip) and then the hand grip coveris rotated closed about the hinge. Finally, the hand grip cover is movedbackward along the hinge axis until the spring loaded button catchengages the cover to secure it in place. This movement of the hand gripcover along the hinge axis also serves to push the fuel cartridge withinthe grip such that the valved port of the fuel cartridge engages themating port to the fuel regulator assembly within the grip of the tool.Those skilled in the art will appreciate that this integrated design ofthe hand grip and fuel storage, loading and unloading mechanism allowsfor convenient loading and unloading of a fuel cartridge. Notably, thereare no separable parts which would need to be temporarily removed whenthe fuel cartridge is replaced (which could then be lost or broken).

Another significant feature of embodiments of the invention involves aconveniently removable cylindrical subassembly which incorporates amajority of the fuel system components. This cylindrical subassembly isintegrated into the hand grip (parallel to the fuel cartridge location)and installed into an extruded subhousing, e.g. from aluminum whichincludes a bore for the cylindrical subassembly. The cylindricalsubassembly includes a venturi or fuel nozzle and a metering valve.These elements can be readily installed or removed for repair orreplacement into the bore into the end of the handle. The fuel nozzlehas a smaller diameter and is installed in the bore first. The meteringvalve, having a wider diameter is properly located by a step within thebore. The entire cylindrical subassembly is then held in place by fuelpressure regulator cap subassembly which engages the port of the fuelcartridge (disposed adjacent and parallel to the cylindricalsubassembly) and directs the regulated fuel into the metering valve.Finally, a simple rear handle end cap is used to secure all thecomponents (fuel nozzle, metering valve, and fuel pressure regulator) inplace. Those skilled in the art will appreciate that the overall designof these components affords ease of maintenance.

FIG. 6A illustrates a bi-directional belt clip assembly of an exemplarycombustion driven fastener hand tool embodiment of the invention. Anadditional feature is incorporated into the rear handle end cap 602.This hand end cap 602 includes a belt clip 604 extending from one sideof the handle which bends to parallel the grip portion 104. The bottomplate 606 of the end cap 602 can be secured by screws 608 in a symmetricpattern such that the same end cap 602 may be installed in two alternatepositions. In one position the belt clip extends along the left side ofthe grip (left image of FIG. 6A) and in the other position the belt clipextends along the right side of the grip (right image of FIG. 6A). Thisallows a user to select which side he prefers the belt clip to belocated.

FIGS. 6B-6E illustrate detailed views of a fuel mixing and transportassembly of an exemplary combustion driven fastener hand tool embodimentof the invention. As previously described, an extruded hand grip section206 can be employed in the grip portion 104. This hand grip section 206can be produce having a cylindrical bore which is used to house the fuelcomponents of the hand tool. Three distinct fuel components can beinstalled in the end of the hand grip into the hand grip section 206.The fuel nozzle 620 and the metering valve 622 fit directly into thecylindrical bore of the hand grip section 206. The larger diameter ofthe metering valve 622 allows it to be aligned into position against anindexing step cut into the bore of the hand grip section 206. Finally, apressure regulator 624 is installed over the metering valve 622 and heldin place by the end cap 602. The pressure regulator 624 receives thevalved port of the adjacent fuel cartridge and directs thepressure-regulated fuel to the metering valve 622.

It should be noted that charging of the combustion chamber with fuel andair is activated by moving the end of the fuel nozzle 620 closest to thefront body section backward toward the end of the hand grip by lever1316 which extends from the fuel nozzle 620 through a wall of the boreof the hand grip section 206. (See FIGS. 7A and 7B.) This is performedthrough operation of the fuel charging-safety linkage describedhereafter in section 10. The design of the fuel nozzle 620 and meteringvalve 622 within the cylindrical bore enables this action to release thepressurized fuel through the fuel nozzle 620 and entrain air beforeflowing through the pathway to the combustion chamber. The fuel chargingsystem elements are arranged to provide very reliable operation suchthat the metering valve 622 closes off the input fuel prior to openingthe output end of the fuel nozzle 620. The cylindrical cavity of thehand grip section 206 for the fuel system components also enablesinexpensive manufacturing of the cylindrical fuel nozzle 620 andmetering valve 622 as these components can be produced using anautomated lathe. In addition, these components afford versatility asthey have potential to be used in other designs as standard components.Details of the fuel system and its operation delivering fuel from thefuel cartridge to the pathway to the combustion chamber are describedhereafter.

Referring first to FIG. 6D, section A-A, the pressure regulator 624operates with a port 630 which receives the valved port of the fuelcartridge when it is installed in the grip as previously described. Theport 630 and storage location for the fuel cartridge is designed to holdthe valved port of the fuel cartridge in an open position so thatpressurized liquid fuel is constantly directed into the sealed space ofthe orifice 632 (using O-ring seals around the valved port of the fuelcartridge). The passage of the small orifice 632 allows fuel to passthrough only in a gaseous state. Following the orifice 632, the gaseousfuel is metered through a pressure regulating valve 634. Typically, aknown schrader valve, commonly used in bicycle tires and many industrialproducts to provide a valve for gases, and easily installed into aninternally threaded hole. Pressure from the gaseous fuel behind thevalve 634 closes it as it pushes the pin 636 forward (to the right).Accordingly, the valve 634 can be opened by pushing the pin 636 backward(to the left). The valve 634 operates to release the gaseous fuel aspecified pressure based on the amount of force applied to the pin 636against the gas pressure. The force on the pin 636 is provided by abiasing spring 638 which pushes against a cylindrical cap 640 that inturn pushes the end of the pin 636. The gaseous fuel is only allowed topass through the valve 634 at a pressure determined by the force of theappropriately designed spring 638 and into the annular space surroundingthe valve 634. An o-ring seal 644 in a outer diameter groove of the cap640 isolates the gaseous fuel. In use, the spring 638 is undercompression between the cap 640 and the installed end cap 602. See e.g.FIG. 6A. The pressure-regulated gaseous fuel is allowed through apassage 642 to the metering valve 622.

Referring back to FIG. 6B, section A-A, the metering valve 622 receivesthe pressure-regulated gaseous fuel at the sealed port 646. The port 646has a face o-ring seal 648 against the body of the pressure regulator624. As previously mentioned, the metering valve 622 and the fuel nozzle624 operate together in a cylindrical space within the hand grip. Themetering valve 622 essentially comprises a cylindrical housing 650 witha cap 652A, 652B at each end and a central dual valve stem 654. Thenovel design employs a common cap 652A, 652B that can be used at eitherend of the housing 650. On the inlet side, a groove in the cap 652 a isused for the O-ring seal 648. On the outlet side, however, the samegroove in the cap 652B is used as a seat for the biasing spring 656against the fuel nozzle 620. Use of a common part for the caps 652A,652B reduces the overall manufacturing costs.

Metering of a fuel charge for combustion is accomplished by movement ofthe dual valve stem 654. The dual valve stem 654 is shown in section A-Aof FIG. 6B with the inlet valve 658A (on the right side) open and theoutlet valve 658B (on the left side) closed. The valves 658A, 658B arevery similar in design but operate in opposite directions; Fuel flows ina central channel of the inlet valve 658A and then through one or moreradial pathways into a small annular space between two a-ring seals.When the dual valve stem 654 is pushed fully left (by fuel pressureagainst the right end of the stem 654), a wide step of the stem 654 onthe left side stops against the inner end of the cap 652B and the inletvalve 658A is open. The open position of the inlet valve 658A allowsjust enough clearance between the inner O-ring of the two o-ring sealsand a chamfered internal diameter of the cap 658A for the fuel to flowfreely into the metering volume 660 (the annular space between the stem654 and the inner wall of the cylindrical housing 650). When the safetylinkage is operated (as described hereafter), the fuel nozzle 620 ispushed to the right (overcoming the combined resistive forces of thebiasing spring 656 and the fuel pressure against the right end of thedual valve stem 654) to move the dual valve stem 654 to the right.Precise spacing of the inlet and outlet valves 658A, 658B and the lengthof the stein 654 allows movement of the dual valve stem 654 to the causethe inlet valve 658A to close and the then the outlet valve 658B to openin a very precise sequence. The inlet valve 658A is closed as the innerO-ring of the two O-ring seals bounding the radial pathway(s) (on theright side of the stern 654) recedes into the chamfered internaldiameter of the cap 658A and just before the outlet valve 658B is movedenough to create clearance between the inner O-ring of the two O-ringseals (on the left side of the stem 654) and a chamfered internaldiameter of the cap 658B for the fuel to flow freely past the o-ring andinto the one or more radial pathways of the stem 654 leading to thecentral channel on the left end of the dual valve stem 654. In thismanner, only the amount of fuel which is temporarily isolated within themetering volume 660 is allowed to proceed out the left central channelof the dual valve stem 654 to the fuel nozzle 620.

The gaseous fuel charge from the central channel of the dual valve stem654 of the metering valve 622 is directed into a sealed channel to anorifice 662 at the right end of the fuel nozzle 620. Past the orifice662, the gaseous fuel enters a venturi region 664 where the fuel becomesentrained with air. From there, the fuel and air mixture moves through awider central channel of the fuel nozzle 620 and out the end to the leftto enter the pathway, past the baffle (described hereafter), and intothe combustion chamber of the front end section previously described.

FIG. 6E shows the fuel nozzle 620 and metering valve 622 before andafter charging the combustion chamber with the fuel and air mixture. Thetop panel shows the system before charging with the fuel nozzle 620 andthe dual valve stem 654 of the metering valve 622 pushed to the left(toward front body section). As discussed above, in this position theinlet valve 658A is open so that fuel flows from fuel cartridge 670through the pressure regulator 624 and into the metering volume 660 ofthe metering valve 622. The bottom panel shows the system aftercharging. The safety linkage (described hereafter) has been actuated topush the roller bushing 1314 to the right against a lever 1316 affixedto the fuel nozzle 620 (through a wall of the hand grip section 206).The body of the fuel nozzle 620 moves to the right compressing thebiasing spring 656 and moving the dual valve stem 654 of the meteringvalve 622 to the right. Movement of the dual valve stem 654 to the rightcauses the inlet valve to close and then the outlet valve to open asdescribed above allowing gaseous fuel from the metering volume 660 toflow out through the venturi of the fuel nozzle 620 and become entrainedwith air and flow on through the pathway to the combustion chamber.

It should also be noted that the requirements for sealing the fuelsystem vary along the fuel and fuel and air mixture path. For example,the fuel path beginning from the fuel cartridge port to the pressureregulator and through the metering valve and fuel nozzle must have goodseals to prevent leakage of the fuel in more liquid form. However, thefuel and air mixture path following the fuel nozzle and up to thecombustion chamber does not require good seals; the air and fuel mixturewill not leak through ordinary joint contacts in most cases. Thecombustion and piston chambers, however, again need good seals in orderto efficiently contain and direct the pressure from combustion to thepiston. Those skilled in the art will appreciate the differentrequirements for seals for each portion of the fuel system as describedhere and select suitable solutions without undue experimentation.

4. Igniter for Combustion Driven Fastener Hand Tool

Another feature that embodiments of the invention can incorporateinvolves the fuel ignition system. Embodiments of the invention canemploy a single unit igniter component which incorporates both anelectrical ignition switch and a spark point. The single unit ignitercan be configured having an elongated main section with the electricalignition switch at one end. The spark point is disposed in the end of asecondary section that extends laterally from the main section.Electrical connections to both the spark point and the electricalignition switch are coupled to the ignition control electronics moduledisposed elsewhere within the hand tool. The electrical ignition switchmay be an optical switch for improve reliability. The spark point cancomprise an exposed conductive end, e.g. metal, within a cylindricalinsulator. In operation, when the electrical ignition switch is closed,sensed by the ignition control electronics module, the ignition controlelectronics module then sends a high voltage pulse to the spark point.

FIG. 7C illustrates an integrated ignition switch and spark point of anexemplary combustion driven fastener hand tool embodiment of theinvention. The igniter component 700 comprises both an ignition switch702 and an ignition spark point 704 in a single housing as describedabove.

Embodiments of the invention can also employ a disc built into a valvestem within the combustion chamber to aid control of the spark used forignition of the fuel and air mixture. There are a number of advantagesderived from the use of this disk. In general, the valve to thecombustion chamber opens to allow the fuel and air mixture to enter thecombustion and is then closed prior to ignition of the fuel and air inthe combustion chamber. The basic valve design comprises a cylindricalelement having an O-ring seal. Smaller diameter stems extend from thiscylindrical element in both directions and are used to support andmanipulate the valve. In addition, the valve is also conductive and usedto close the sparking circuit; a spark is generated between the sparkpoint (of the igniter component) and the disc on the valve stern toignite the fuel and air mixture within the combustion chamber.

Employing the disk on the valve stem allows the spark point on theigniter component to be disposed closer to the wall of the combustionchamber. Thus, the spark point of the igniter component does not extendinto the interior of the combustion chamber and can be shortened to bevirtually flush with the combustion chamber wall. Accordingly, the sparkpoint of the igniter component does not obstruct removal or installationof the valve or other components within the combustion chamber. Inaddition, position of the disc on the stern sets the spark locationclose to the end of the combustion chamber. Accordingly, combustionefficiency is improved because the flame front during combustion movessubstantially in one direction away from the spark and toward the pistoncylinder. In contrast, if the spark were generated in the middle of thecombustion chamber a pair of flame fronts would move in oppositedirections with only one moving toward the piston chamber, greatlyreducing the combustion efficiency.

FIGS. 7A and 7B illustrate cutaway views of a fuel charging operation ofan exemplary combustion driven fastener hand tool embodiment of theinvention. FIG. 7A shows the combustion chamber valve 720 in the openposition with the valve stem disc 722 for spark generation. Note thevalve stem disc is disposed above the spark point 704 of the ignitercomponent 700. FIG. 7B shows the combustion chamber valve 720 in theclosed position with the valve stem disc 722 for spark generation. Thechamber valve 720 is closed by the user pulling the trigger 106 towardthe hand grip. The trigger 106 has a pinned joint 724 at a front endcoupled to a sliding link 726 which is coupled to the chamber valve 720.Here the valve stein disc is disposed in line with the spark point 704of the igniter component 700 providing the closest separation for sparkgeneration.

5. Replaceable Piston Driver for Combustion Driven Fastener Hand Tool

Another feature of embodiments of the invention enables convenientreplacement of the primary wearable component of the hand tool. The dualchambers (which are formed by the bores of the front body sectionpreviously described) are easily accessible for service and replacementof components. The piston driver of the combustion driven fastener handtool typically is the primary wearable component due to its repeatedstriking of the fasteners. Accordingly, it is expected that the pistondriver will be replaced more frequently than other components. Thus, thehand tool design incorporates features which allow very convenientreplacement of piston driver. A top cap assembly of the front bodysection is designed such that it can be removed in one piece afterremoving a set of fasteners, e.g. six screws. Removal of the top capassembly provides direct access to the piston driver so that it can beeasily replaced. Access to both the piston and combustion chambers isprovided.

FIG. 8 illustrates a dual chamber assembly of an exemplary combustiondriven fastener hand tool embodiment of the invention. The exploded viewshows the parts as they will be installed. The piston driver 802 whichmay need occasional replacement is installed directly into the firstchamber and the valve 720 and stem assembly is installed directly intothe second chamber Both chambers are closed and sealed together byinstallation of the top cap assembly 804 which is held in by a set ofidentical fasteners 806, e.g. screws.

6. Unitary Fuel Passage Baffle for Combustion Driven Fastener Hand Tool

Embodiments of the invention can also employ an\ novel air and fuelmixing baffle within the pathway between the fuel nozzle and thecombustion chamber. The mixing baffle creates turbulent flow of the airand fuel enabling improved mixing as the fluid moves through the pathwayand into the combustion chamber. The design of the mixing baffle takesadvantage of a turn in the pathway. Accordingly, the mixing bafflecomprises a flat plate of material, e.g. metal, having a plurality ofcuts on one side to yield a plurality of separate flaps. Alternate flapsare bent to partially obstruct the pathway on one side the turn, whereasunbent flaps partially obstruct the pathway on the other side of theturn. The simple design enables a mixing baffle to be very cheaplymanufactured. In addition, tuning of the design is similarly made veryconvenient as the mixing baffle can be quickly altered in development.

FIGS. 9A-9C illustrates a unitary fuel passage baffle 900 of anexemplary combustion driven fastener hand tool embodiment of theinvention. It will apparent to those skilled in the art that the baffle900 can be readily constructed from flat sheet material, e.g. metal,having slots cut to form a plurality of flaps. In the exampleembodiment, five flaps 902, 904 are shown although any number of flapsmay be employed for a specific design. Alternating flaps 902 are bentsuch that when the baffle 900 is installed in a pathway turn one set offlaps 904 partially obstruct the pathway on one side of the turn and theother set of flaps 902 partially obstruct the pathway on the other sideof the turn. FIGS. 9B and 9C show the installation location of theexample embodiment where the set of three flaps 904 partially obstructsthe fuel and air mixture pathway as it moves down the pathway and theremaining set of two flaps 902 partially obstructs the pathway after itturns to enter the primary combustion chamber.

7. Ignition Battery Compartment for Combustion Driven Fastener Hand Tool

Embodiments of the invention can also employ a novel battery storage.The hand tool can employ an electronic combustion ignition system whichemploys nominal battery power. As previously described, the batterycarrier section can be located at the end of the the hand grip. Thebattery carrier section extends from the end of the grip portion towardsthe end of the fastener strip carrier. In this manner, the batterycarrier section also provides additional structural support for thefastener strip carrier. In addition, the battery carrier section canemploy a sliding cover, which can be pinned to rotate about one point,e.g. with a first screw, and secured at another point, e.g. with asecond screw. A power switch for the hand tool ignition system can alsobe disposed on the side opposite the cover.

FIG. 10 illustrates an ignition battery compartment and access of anexemplary combustion driven fastener hand tool embodiment of theinvention. The battery carrier section 110 includes a sliding cover 1002which is pinned to rotate about a first point 1002 when a fastener isremoved from a second point 1006. The sliding cover 1002 slides into apocket of the battery carrier section 110 having a narrower width at thedeepest edge of the pocket and a wider width at the opening edge. Notethat FIG. 10 does not show the bracket 112 coupled between the batterycarry section 110 and the fastener strip carrier 108 to reinforce theoverall structure as shown in FIGS. 1B and 1E. On the side opposite thecover 1002, a power switch 1008 can be disposed for turning on power tothe ignition circuit.

8. Piston Bumper for Combustion Driven Fastener Hand Tool

FIG. 11 illustrates replaceable piston bumper element of an exemplarycombustion driven fastener hand tool embodiment of the invention. Thepiston bumper 1102 is another wearable part (similar to the pistondriver 802) which undergoes repeated impacts which must occasionally bereplaced. In order to make replacement easy the piston bumper 1102 isreadily removable after the top cap assembly 804 and piston driver 802have been removed. See section 5 above. The piston bumper 1102 isinstalled into the open end of the piston bore and a clip 1104(“U-clip”) is installed into a slot in the side of the cast housing. Theclip 1104 has an interior semi-circular edge 1106 which engages a groove1108 in the piston bumper 1102 locking it into place. The piston driver802 and top cap assembly 804 are then installed over the bumper 1102.

9. Exhaust Valves for Combustion Driven Fastener Hand Tool

Exhaust valves are employed to allow the combustion gases to be ejectedafter driving the fastener. After abruptly closing, negative pressuretrapped in the piston chamber causes the piston driver to return to thestart position. Stops and standoffs can be integrated directly into theexterior housing to control operation of the valves.

FIGS. 12A-12C illustrate exhaust valves of an exemplary combustiondriven fastener hand tool embodiment of the invention. The combustiondriven fastener hand tool can also incorporate a novel exhaust valvedesign. The exhaust valves 1202A, 1202B can be implemented as reedvalves comprising a flat length of material, e.g. metal, secured at oneend, e.g. with a stiffener and fasteners 1210A, 1210B. Exhaust gasesfrom the piston chamber are directed through ports 1204A, 1204B in theprimary housing 204A, 204B when the tool is operated. The opening gap ofthe valves 1202A, 1202B is controlled by stops 1210A, 1210B integratedinto the interior surface of the exterior housing 402A, 402B. Each stop1210A, 1210B can comprise a ramped section centered along the valvelength which has a lowest end at the valve opening end. The exteriorhousing 402A, 402B also incorporates incorporates standoffs 1208A, 1208Bin the interior wall. The standoffs and stops precisely set the valveopening gap in operation. As previously mentioned, the exterior housingcan be produced as a molded plastic component.

10. Fuel Charging Safety Linkage for Combustion Driven Fastener HandTool

An embodiment of the invention can also incorporate a novel safetylinkage used in the operation of the tool. The nose piece of the toolwhich contacts the point where a fastener is to be driven includes asliding link which moves linearly toward and away from the workpiecesurface in a channel within the nose piece. This linear motion istransmitted to an armature which has a slotted joint coupled to theopposite end of the sliding link. The armature rotates about a pinnedjoint and has an opposite end which pushes a valve causing it to openand charge combustion chamber with a fuel and air mixture.

FIGS. 13A-13D illustrate fuel charging, safety linkage, and triggerlockout of an exemplary combustion driven fastener hand tool embodimentof the invention. The sliding link 1302 of the nose piece 1300 is heldin a channel and allowed to move linearly. One end of the sliding link1302 can be pressed against a work piece surface (to be fastened) andthe other end is coupled to an armature 1304. The coupling to thearmature 1304 can be implemented through a slotted joint 1306 comprisinga roller bushing 1308 coupled to the end of the sliding link 1302 whichrolls in the slot of the armature 1304 reducing friction and eliminatingany binding of the joint in use. The armature 1304 has a pinned joint1310 about which it rotates under action from the sliding link 1302. Thearmature 1304 further includes a distal end 1312 which pushes againstthe fuel nozzle to charge the combustion chamber. See section 3 above,FIGS. 6B-6D, and FIGS. 7A-7B. The distal end 1312 is coupled to a wideroller bushing 1314 to provide rolling contact against the lever 1316 ofthe fuel nozzle reducing friction and eliminating any binding of thejoint in use. It should be noted that return of the armature 1304 andsliding link 1302 to their original positions (with the sliding link1304 extended) is provided by spring loading within the the nozzle andmetering assembly.

As previously described, operation of the combustion driven fastenerhand tool to drive a fastener is performed in two steps. The defaultstate of the hand tool with a fuel cartridge 670 loaded is forpressurized fuel to occupy the metering volume 660 of the metering valve622 (flowing through the pressure regulator 624 from the fuel cartridge670). First the safety linkage is operated by pressing the sliding link1302 against a work surface causing pressurized fuel to move (by closingthe inlet valve 658A and opening the outlet valve 658B) from themetering volume 660 through the fuel nozzle 620 and through the fuel andair mixture pathway, past the fuel and air baffle and the open valve 720and into the combustion chamber. Next, with the hand tool still heldagainst the work surface to hold the inlet valve 658A closed, the userpulls the trigger 106 towards the hand grip causing the combustionchamber valve 720 to first close and then the triggering the ignitionswitch at the end of travel which causes a spark to be generated betweenthe spark point and the disc on the valve stem as previously described.See section 4 and FIGS. 7A and 7B. If the safety linkage is notoperated, however, embodiments of the invention can employ a triggerlockout mechanism to prevent any possible ignition.

FIG. 13D shows the trigger lockout for an exemplary embodiment of theinvention. The trigger is prevented from activating the ignition byemploying the fuel nozzle lever 1316 to properly locate a pivot point1318 for a pin 1320 on the trigger 106. The bottom panel shows the fuelnozzle lever 1316 pushed into the proper position by the roller bushing1314 of the safety linkage to position the pivot point 1318 on the lever1316 directly adjacent to the pin 1320 of the trigger 106. Accordingly,when the trigger 106 is pulled in with the lever 1316 in this position,the pinned joint 724 of the trigger will move downward a sufficientdistance to close the chamber valve and trigger the ignition switch.(See section 4 and FIGS. 7A and 7B.) However, is the safety linkage isnot actuated first as shown in the top panel, the pivot point 1318 willnot be located adjacent to the pin 1320 of the trigger 106. In thiscase, pulling on the trigger 106 will move the pin 1320 upward into arecess behind the pivot point 1318 of the level 1316 and the pinnedjoint 724 will not move downward enough (if at all) to trigger theignition switch.

This concludes the description including the preferred embodiments ofthe present invention. The foregoing description including the preferredembodiment of the invention has been presented for the purposes ofillustration and description. It is not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible within the scope of the foregoing teachings.Additional variations of the present invention may be devised withoutdeparting from the inventive concept as set forth in the followingclaims.

What is claimed is:
 1. A combustion driven fastener apparatus,comprising a fuel system subassembly including: a fuel nozzle having ametered fuel input port and fuel and an air mixture output port, thefuel nozzle disposed in a bore of the combustion driven fastenerapparatus; and a metering valve having a fuel input port and a meteredfuel output port, the metering valve disposed in the bore with themetered fuel output port coupled to the metered fuel input port, themetering valve comprising a hollow cylindrical housing having a cap ateach end and a central dual valve stem therebetween; wherein movement ofthe dual central valve stem closes an inlet valve at one end and opensan outlet valve at an opposite end in a coordinated manner to release ametered amount of fuel through the outlet valve while preventingadditional fuel through the inlet valve.
 2. The apparatus of claim 1,wherein the bore includes a step to locate the metering valve at a setposition along a length of the bore.
 3. The apparatus of claim 1,wherein the fuel nozzle and the metering valve are cylindricallyconfigured and the metering valve has a larger maximum diameter than thefuel nozzle.
 4. The apparatus of claim 1, wherein the cap at each endcomprises a common cap design having an annular groove.
 5. The apparatusof claim 1, wherein the fuel system subassembly further includes abiasing spring disposed between the fuel nozzle and the metering valveand moving the fuel nozzle towards the metering valve compresses thebiasing spring therebetween such that the metered fuel input port of thefuel nozzle pushes against the metered fuel output port of the meteringvalve causing the movement of the dual central valve stem.
 6. Theapparatus of claim 1, wherein fuel pressure behind the fuel input portof the metering valve forces the dual central valve stern such the thatinlet valve is normally open and the outlet valve is normally closed. 7.The apparatus of claim 1, wherein the fuel system subassembly furtherincludes a pressure regulator having a fuel cartridge input port and afuel output port, the fuel output port coupled to the fuel input port ofthe metering valve.
 8. The apparatus of claim 7, wherein the pressureregulator is disposed in the bore.
 9. The apparatus of claim 1, whereinthe bore is disposed in a hand grip section of the combustion drivenfastener apparatus.
 10. The apparatus of claim 9, further comprising acap fastened over the bore of the hand grip section to secure the fuelsystem subassembly in place, the cap including a clip portion extendingfrom an end of the hand grip section adjacent and parallel along a sideof the hand grip section.
 11. A method of making a combustion drivenfastener apparatus, comprising a fuel system subassembly including:disposing a fuel nozzle in a bore of the combustion driven fastenerapparatus, the fuel nozzle having a metered fuel input port and fuel andan air mixture output port; and disposing a metering valve in the borebehind the fuel nozzle with the metered fuel output port coupled to themetered fuel input port, the metering valve having a fuel input port anda metered fuel output port, the metering valve comprising a hollowcylindrical housing having a cap at each end and a central dual valvestem therebetween; wherein movement of the dual central valve stemcloses an inlet valve at one end and opens an outlet valve at anopposite end in a coordinated manner to release a metered amount of fuelthrough the outlet valve while preventing additional fuel through theinlet valve.
 12. The method of claim 11, wherein the bore includes astep to locate the metering valve at a set position along a length ofthe bore.
 13. The method of claim 11, wherein the fuel nozzle and themetering valve are cylindrically configured and the metering valve has alarger maximum diameter than the fuel nozzle.
 14. The method of claim11, wherein the cap at each end comprises a common cap design having anannular groove.
 15. The method of claim 11, wherein the fuel systemsubassembly further includes a biasing spring disposed between the fuelnozzle and the metering valve and moving the fuel nozzle towards themetering valve compresses the biasing spring therebetween such that themetered fuel input port of the fuel nozzle pushes against the meteredfuel output port of the metering valve causing the movement of the dualcentral valve stem.
 16. The method of claim 11, wherein fuel pressurebehind the fuel input port of the metering valve forces the dual centralvalve stem such the that inlet valve is normally open and the outletvalve is normally closed.
 17. The method of claim 11, wherein the fuelsystem subassembly further includes a pressure regulator having a fuelcartridge input port and a fuel output port, the fuel output portcoupled to the fuel input port of the metering valve.
 18. The method ofclaim 17, wherein the pressure regulator is disposed in the bore. 19.The method of claim 11, wherein the bore is disposed in a hand gripsection of the combustion driven fastener apparatus.
 20. The method ofclaim 19, further comprising fastening a cap over the bore of the handgrip section to secure the fuel system subassembly in place, the capincluding a clip portion extending from an end of the hand grip sectionadjacent and parallel along a side of the hand grip section.